A first conventional fuel oil gasifying system disclosed in a Taiwan patent of No. 431575 for a gas burning system shown in FIG. 1 includes a tank (A) provided with a check window (A1), a gas outlet (A2), a gas valve (A3), a valve cap (A30) screwed on the tank (A), a joint (A31) with a valve (A32) connected with the valve cap (A30). The valve (A32) has a gas passageway (A33) with its upper end communicating with the joint (A31) and with its lower end screwed with an inner pipe (A34) extending down near to the bottom of the tank (A). The inner pipe (A34) has an upper end portion with a larger diameter than that of the inner pipe itself for a valve stop (A35) to be positioned therein in a normally-open condition by its weight to keep the intake passageway (A33) normally open, with its bottom provided with a gasket to lift a bit to keep the upper end portion normally communicating with the inner pipe itself. Further, an outer pipe (A36) is provided to be located lengthwise outside of the inner pipe (A34), having a bit shorter length than the inner pipe (A34) but a larger diameter to define an annular passageway between the two pipes (A34) and (A36). Then an electric pump (A37) is connected with the gas valve (A3) by means of a rubber tube (A360) to send compressed air through the gas valve (A3) into the tank (A) to gasifying the fuel oil in the tank (A) and let it flow out of the outlet.
Next, a second conventional gas supplying system disclosed in a Taiwan patent of No. 452052 shown in FIG. 2 includes a tank (B) provided with a guide tube (B0), a backflow stop valve (B1) fixed on the guide tube (B0), a cross-shaped branch tube (B2) connected with the lower end of the guide tube (B0), a bubble stone fixed in each end of the cross-shaped tube (B2), and a controller (B3) connected with the tank (B) with two tubes. The controller (B3) includes a pressure control circuit and a drive motor. The motor is connected with a switch valve and communicates with an outer guide tube. The pressure control circuit stabilized the gas pressure in the tank (B) at a definite value. Thus, when compressed air is sent through the outer guide tube and into the guide tube (B0) in the tank (B), and then passes through the bubble stones to force the liquid fuel oil to bubble and let the liquid gas vaporize and be sent out for burning.
It can be seen that the second conventional case and the first conventional case are almost the same, using a electric pump or a motor for adding pressure to the fuel oil for vaporizing and sending it out for burning.
However, the first and the second conventional case use the way of adding pressure to the tank and mixing air and gas for a burning appliance to burn, with first vaporization and subsequent burning suitable for common gas or comparatively fluidly fuel oil, but not for low fluidly heavy oil, which needs preliminary heating and standby.